1. Field of the Invention
The present invention relates to photoresist monomers suitable for a bilayer photoresist, polymers derived therefrom and photoresist compositions comprising such polymers. In particular, the present invention relates to photoresist monomers comprising a silicon moiety.
2. Description of the Background Art
Some semiconductor manufacturing processes use photoresist copolymers derived from a monomer comprising an alicyclic compound to form ultrafine patterns. However, the yield of photoresist polymers from these compounds is relatively low resulting in increased manufacturing costs. While the yield of acrylates polymerization is high, the resulting photoresist polymers have a weak etching resistance, thereby limiting its use.
Forming an ultrafine pattern below 0.13 m using a conventional photoresist coating thickness results in a high aspect ratio which may cause the pattern to collapse. And if the coating thickness is reduced, the resulting photoresist coating often has low or no etching resistance. Thus, it is difficult to perform following, or successive processes after etching process using conventional photoresist polymers.
One method for overcoming the above described limitations is to use a xe2x80x9cthin resist-hard maskxe2x80x9d process, which generally involves reducing a coating thickness of the photoresist composition and introducing a hard mask below the photoresist film coating. Another method is to use a bilayer photoresist comprising silicon, which involves coating a bottom anti-reflective coating material (BARC), g-line photoresist or i-line photoresist on the substrate and then coating a silicon comprising photoresist thereon. The resulting photoresist film is exposed, and the upper layer (i.e., photoresist comprising silicon) is wet developed to form an upper layer photoresist pattern. The lower layer is dry developed using O2 plasma and the upper photoresist pattern as a mask to form a lower layer resist pattern. This process reduces or eliminates the occurrence of photoresist pattern collapse.
It is therefore an object of the present invention to provide a photoresist monomers comprising silicon, photoresist polymers for bilayer resist derived from the same, and a process for preparing such photoresist polymers.
Another object of the present invention is to provide photoresist compositions comprising such photoresist polymers.
Still another object of the present invention is to provide a semiconductor device produced by using such a photoresist composition.